Decades of data on more 3,000 participants reveal that people born in the same time period share a similar correlation between body mass index and a gene linked to obesity. The lack of impact of the “obesity gene” to people born before 1942 suggests that genetic and environmental factors interact differently at different times to influence obesity risk. The findings were Proceedings of the National Academy of Sciences this week.
Researchers revealed in 2007 that people with a common variant of the FTO gene tended to be heavier than people without it, and multiple studies have since supported this link, New York Times explains. Two copies of the risky variant of the gene could add seven extra pounds and increase that person’s obesity risk by 50 percent.
However, most gene-environment interaction studies have focused on differences between people in the same birth cohort -- groups who were born during certain time spans. So, to account for bigger environmental changes over time, a team led by James Rosenquist of Massachusetts General Hospital analyzed data from the Offspring Cohort of the Framingham Heart Study collected between 1971 and 2008. The team looked specifically at that particular genetic variant and the separate effects of various environmental and demographic factors on body mass index (BMI). This common measure of obesity was measured eight times during the study period of nearly 40 years.
“The correlation between the best known obesity-associated gene variant and body mass index increased significantly as the year of birth of participants increased,” Rosenquist says in a news release. “These results -- to our knowledge the first of their kind -- suggest that this and perhaps other correlations between gene variants and physical traits may very significantly depending on when individuals were born, even for those born into the same families.”
They found no correlation between the obesity-risk variant and BMI for people born before 1942. In participants born after 1942, on the other hand, the correlation was twice as strong as previously reported results. The team wasn’t able to identify the specific reasons behind this increased obesity risk, though they think it could be due to our increased reliance on technology (instead of physical labor) and the availability of high-calorie processed foods in the post-World War II era.
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